WASHINGTON — The chairman of the House Benghazi Committee had a message Sunday for his GOP colleagues: “Shut up talking about things that you don’t know anything about.”

Rep. Trey Gowdy (R-SC) insisted he’s running an important, fact-based investigation into the Sept. 11, 2012, terrorist attacks in Libya, but has been undermined by comments from colleagues that the committee has been politically motivated to attack Hillary Clinton.

“Unless you’re on the committee, you have no idea what we’ve done, why we’ve done it, and what new facts we have found,” Gowdy said on CBS’ “Face the Nation” in response to criticism from Reps. Kevin McCarthy and Richard Hanna and a former committee investigator.

Also Sunday, Gowdy and the top Democrat on the committee, Rep. Elijah Cummings, tussled over letters and dueling TV interviews over the purpose of the committee’s work and accusing each other of making false claims about classified information. The latest distraction helped undermine Clinton’s appearance before the committee on Thursday.

“I think that there are stakes for her, but they’ve been reduced by the kind of circus around this committee,” said Democratic strategist David Axelrod.

For her part, Clinton said she doesn’t have much more to say about the terrorist attack that killed four Americans.

“I testified to the best of my ability before the Senate and the House. I don’t know that I have very much to add. This is, after all, the eighth investigation,” she told CNN’s “State of the Union.”

“I really don’t know what to expect. I think it’s pretty clear that whatever they might have thought they were doing, they ended up becoming a partisan arm of the Republican National Committee with an overwhelming focus on trying to, as they admitted, down my poll numbers.”

Democrats have charged the committee has focused too much on Clinton’s emails instead of others in defense and intelligence gathering that could offer insight on the terrorist attack.

Cummings, the Maryland Democrat, said the upcoming hearings mark a “sad day for all of us because we made a commitment to the families,” Cummings told “Face the Nation.” “The families came in with tears in their eyes literally and said, ‘Please do not make this a political football.’ That’s exactly what’s happened.”

Without the committee’s work, Gowdy said, they would have never discovered Clinton emails related to the attacks as wells as emails from Ambassador Chris Stevens, who was killed at the diplomatic facility.

“We have 50,000 new documents,” Gowdy said. “Less than 5 percent have anything to do with Secretary Clinton. She’s an important witness, but she is one witness and by the time we’re through, John, we’ll have interviewed 70 witnesses.”

The committee was launched 17 months ago and it’s unclear when a final report will be complete. One GOP member of the panel blamed the delay on Democrats.

“What’s taken us so long is the Democrats on the committee and this administration have played ‘hide the ball’ and have denied us records that the American people deserve and that our committee needs to complete our investigation,” Rep. Mike Pompeo (R-Kan.) said on NBC’s “Meet the Press” on Sunday. “We would have been happy to move more quickly, but we’ve met with obstruction all along the way.”